Update: If anyone else is interested – Mr. Gustavo sent us the login credentials. After log into his dashboard, I noticed that in the Info > Discount Pricing Table > Single product page > “Template for non-variable products” and “Template for variable products” fields, he was using the [alg_wc_product_ppq_table] shortcode without adding any parameters into it. As a result, I modified the shortcode to
[alg_wc_product_ppq_table table_format="vertical" heading_format="desde %level_min_qty% uds." price_row_format="%new_price_single%"]
and it seems to fix the issue.